I ran into this problem awhile ago. Here is how I solved it:
SELECT
p.ProblemType AS "td"
, '' AS "text()"
, p.Onset AS "td"
, '' AS "text()"
, p.DiagnosisStatus AS "td"
FROM tblProblemList p
WHERE p.PatientUnitNumber = @PatientUnitNumber
FOR XML PATH('tr')